socket.3p (5706B)
- '\" et
- .TH SOCKET "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- socket
- \(em create an endpoint for communication
- .SH SYNOPSIS
- .LP
- .nf
- #include <sys/socket.h>
- .P
- int socket(int \fIdomain\fP, int \fItype\fP, int \fIprotocol\fP);
- .fi
- .SH DESCRIPTION
- The
- \fIsocket\fR()
- function shall create an unbound socket in a communications domain, and
- return a file descriptor that can be used in later function calls that
- operate on sockets. The file descriptor shall be allocated as described in
- .IR "Section 2.14" ", " "File Descriptor Allocation".
- .P
- The
- \fIsocket\fR()
- function takes the following arguments:
- .IP "\fIdomain\fR" 12
- Specifies the communications domain in which a socket is to be
- created.
- .IP "\fItype\fR" 12
- Specifies the type of socket to be created.
- .IP "\fIprotocol\fR" 12
- Specifies a particular protocol to be used with the socket. Specifying
- a
- .IR protocol
- of 0 causes
- \fIsocket\fR()
- to use an unspecified default protocol appropriate for the requested
- socket type.
- .P
- The
- .IR domain
- argument specifies the address family used in the communications
- domain. The address families supported by the system are
- implementation-defined.
- .P
- Symbolic constants that can be used for the domain argument are defined
- in the
- .IR <sys/socket.h>
- header.
- .P
- The
- .IR type
- argument specifies the socket type, which determines the semantics of
- communication over the socket. The following socket types are defined;
- implementations may specify additional socket types:
- .IP SOCK_STREAM 12
- Provides sequenced, reliable, bidirectional, connection-mode byte
- streams, and may provide a transmission mechanism for out-of-band
- data.
- .IP SOCK_DGRAM 12
- Provides datagrams, which are connectionless-mode, unreliable messages
- of fixed maximum length.
- .IP SOCK_SEQPACKET 12
- .br
- Provides sequenced, reliable, bidirectional, connection-mode
- transmission paths for records. A record can be sent using one or more
- output operations and received using one or more input operations, but
- a single operation never transfers part of more than one record. Record
- boundaries are visible to the receiver via the MSG_EOR flag.
- .P
- If the
- .IR protocol
- argument is non-zero, it shall specify a protocol that is supported by
- the address family. If the
- .IR protocol
- argument is zero, the default protocol for this address family and type
- shall be used. The protocols supported by the system are
- implementation-defined.
- .P
- The process may need to have appropriate privileges to use the
- \fIsocket\fR()
- function or to create some sockets.
- .SH "RETURN VALUE"
- Upon successful completion,
- \fIsocket\fR()
- shall return a non-negative integer, the socket file descriptor.
- Otherwise, a value of \-1 shall be returned and
- .IR errno
- set to indicate the error.
- .br
- .SH ERRORS
- The
- \fIsocket\fR()
- function shall fail if:
- .TP
- .BR EAFNOSUPPORT
- .br
- The implementation does not support the specified address family.
- .TP
- .BR EMFILE
- All file descriptors available to the process are currently open.
- .TP
- .BR ENFILE
- No more file descriptors are available for the system.
- .TP
- .BR EPROTONOSUPPORT
- .br
- The protocol is not supported by the address family, or the protocol is
- not supported by the implementation.
- .TP
- .BR EPROTOTYPE
- The socket type is not supported by the protocol.
- .P
- The
- \fIsocket\fR()
- function may fail if:
- .TP
- .BR EACCES
- The process does not have appropriate privileges.
- .TP
- .BR ENOBUFS
- Insufficient resources were available in the system to perform the
- operation.
- .TP
- .BR ENOMEM
- Insufficient memory was available to fulfill the request.
- .LP
- .IR "The following sections are informative."
- .SH "EXAMPLES"
- None.
- .SH "APPLICATION USAGE"
- The documentation for specific address families specifies which
- protocols each address family supports. The documentation for specific
- protocols specifies which socket types each protocol supports.
- .P
- The application can determine whether an address family is supported by
- trying to create a socket with
- .IR domain
- set to the protocol in question.
- .SH "RATIONALE"
- None.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "Section 2.14" ", " "File Descriptor Allocation",
- .IR "\fIaccept\fR\^(\|)",
- .IR "\fIbind\fR\^(\|)",
- .IR "\fIconnect\fR\^(\|)",
- .IR "\fIgetsockname\fR\^(\|)",
- .IR "\fIgetsockopt\fR\^(\|)",
- .IR "\fIlisten\fR\^(\|)",
- .IR "\fIrecv\fR\^(\|)",
- .IR "\fIrecvfrom\fR\^(\|)",
- .IR "\fIrecvmsg\fR\^(\|)",
- .IR "\fIsend\fR\^(\|)",
- .IR "\fIsendmsg\fR\^(\|)",
- .IR "\fIsetsockopt\fR\^(\|)",
- .IR "\fIshutdown\fR\^(\|)",
- .IR "\fIsocketpair\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<netinet_in.h>\fP",
- .IR "\fB<sys_socket.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .